1. Field of the Invention
The present invention relates to a location registration system, a mobile terminal, a control equipment, and methods of location registration in the location registration system, and particularly to methods of determining a location area (which is also called a location registration area) for a mobile terminal.
2. Description of the Related Art
In a mobile communication system comprising a mobile communication network provided with facilities such as base stations and switches, and mobile terminals accommodated in the mobile communication network, the service areas are formed by a plurality of location areas. In such a mobile communication system, so called location registration process is performed to manage information about the location area to which a mobile terminal belongs. In this location registration process, once a mobile station detects a change in location area, it sends a location registration request signal to the mobile communication network.
In conventional mobile communication networks, the size and shape of the location area are uniformly set for all mobile terminals. However, actually the optimal location area varies for each mobile terminal as it depends on the mobility statuses and traffic properties of each terminal. Consequently, in conventional mobile communication systems, a mobile terminal with a fairly large mobility range relative to the size of location area, when moving at a high speed, location registration request signals are sent frequently. On the other hand, when there is a call arrival for the mobile terminal, paging signals are sent to the mobile terminal by way of all the base stations in the location area in which the mobile terminal is located. That is, within the same location area, the same amount of paging traffic arises for a mobile terminal that is not moving at all (remaining stationary over a long time period) and for a mobile terminal moving frequently within the location area. Thus, conventional location registration systems have experienced unnecessary traffic with respect to location registration and paging.
As a technology for solving these problems, the technology as described in Japanese Unexamined Patent Publication No. Heisei 7-322333 is available. In this publication, a location registration controlling scheme is disclosed in which location registration for a mobile terminal is performed along with determination of a location area for the mobile terminal when the mobile terminal detects the need for changing location areas.
However, in the above described publication, an opportunity for location registration arises only when a mobile terminal crosses a location area boundary or when it is remaining stationary in the same cell over a long time period. That is, in the location registration controlling scheme disclosed in the above described publication, information such as a moving speed and a frequency of call arrival measured at a mobile station is sent to the mobile communication network only when the mobile terminal recognizes a need for changing location areas. Thus, the location registration method in which a location area is determined by the mobile communication network based on values measured at the mobile terminal and the location area is sent to the mobile terminal, has a problem in that a location area cannot be set up when the mobile terminal does not detect a change of location area. For example, when a change of location area does not take place as the mobile terminal is moving frequently, but only within a limited range, a location area will not be set up as the mobile terminal does not perform location registration.
An object of the present invention is to provide a location registration system capable of reducing traffic for location registration and paging in the mobile communication network, as well as a mobile terminal, a control equipment, and a location registration method in such a location registration system.
Another object of the invention is to provide a location registration system capable of setting up the optimal location area even when a change of location area does not take place, as well as a mobile terminal, a control equipment, and a location registration method in such a location registration system.